U.S. patent number 6,156,033 [Application Number 09/208,182] was granted by the patent office on 2000-12-05 for ablation catheter having electrode means and methods thereof.
Invention is credited to Weng-Kwen Raymond Chia, Hosheng Tu.
United States Patent |
6,156,033 |
Tu , et al. |
December 5, 2000 |
Ablation catheter having electrode means and methods thereof
Abstract
An improved ablation catheter with a plurality of needles on at
least one electrode suitable for radiofrequency ablation of cardiac
tissues includes a delivery catheter and an inner catheter. The
ablation catheter has a temperature sensor and a closed-loop
temperature controller. The steerable catheter having at least one
electrode includes a plurality of needles, wherein a longitudinal
length of said at least one electrode is 4 mm or longer, a distance
of the needles of the plurality of needles on the at least one
electrode is 2 mm or less, a height of the plurality of needles is
1 mm or less, and wherein the plurality of needles on the at least
one electrode faces a target tissue side.
Inventors: |
Tu; Hosheng (Tustin, CA),
Chia; Weng-Kwen Raymond (Irvine, CA) |
Family
ID: |
25422529 |
Appl.
No.: |
09/208,182 |
Filed: |
December 9, 1998 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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906490 |
Aug 5, 1997 |
5941845 |
|
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856726 |
May 15, 1997 |
5792140 |
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Current U.S.
Class: |
606/41; 607/101;
607/122 |
Current CPC
Class: |
A61B
18/08 (20130101); A61B 18/1492 (20130101); A61B
18/1477 (20130101); A61B 2017/003 (20130101); A61B
2018/00011 (20130101); A61B 2018/00029 (20130101); A61B
2018/00107 (20130101); A61B 2018/00136 (20130101); A61B
2018/00154 (20130101); A61B 2018/00351 (20130101); A61B
2018/00577 (20130101); A61B 2018/00744 (20130101); A61B
2018/00791 (20130101); A61B 2018/00797 (20130101); A61B
2018/00815 (20130101); A61B 2018/00839 (20130101); A61B
2018/0091 (20130101); A61B 2018/1425 (20130101); A61B
2018/143 (20130101); A61B 2018/1432 (20130101); A61B
2018/1467 (20130101); A61B 2218/002 (20130101); A61M
2025/0096 (20130101); A61B 2090/3782 (20160201); A61B
2090/3925 (20160201) |
Current International
Class: |
A61B
18/04 (20060101); A61B 18/14 (20060101); A61B
18/08 (20060101); A61B 018/18 () |
Field of
Search: |
;606/37-41,49,50 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Dvorak; Linda C. M.
Assistant Examiner: Gibson; Roy
Parent Case Text
This is a division of prior application Ser. No. 08/906,490, filed
Aug. 5, 1997, now U.S. Pat. No. 5,941,845, which is a
continuation-in-parts of Ser. No. 08/856,726 filed May 15, 1997,
now U.S. Pat. No. 5,792,140.
Claims
What is claimed is:
1. An ablation catheter comprising:
a delivery catheter having a distal end, a proximal end, and at
least one lumen extending between the distal end and the proximal
end;
a handle attached to the proximal end of the delivery catheter;
an inner catheter located within the at least one lumen of the
delivery catheter, the inner catheter having a distal tip section,
a distal end, a proximal end, and a central lumen extending between
the distal end and the proximal end of the inner catheter, wherein
the distal tip section having at least one electrode; and
a plurality of needles on the at least one electrode, each having a
tip, wherein a longitudinal length of said at least one electrode
is 4 mm or longer, a distance between the tips of the needles is 2
mm or less, a height of each needle is 1 mm or less, and wherein
the plurality of needles on the at least one electrode face a
target tissue side.
2. An ablation catheter as in claim 1 further comprising a steering
mechanism at the handle for controlling deflection of the ablation
catheter.
3. An ablation catheter as in claim 2, wherein the plurality of
needles on the at least one electrode is formed of a metal
mesh.
4. An ablation catheter as in claim 2 further comprising a
closed-loop temperature control mechanism and at least one
temperature sensor mounted on the at least one electrode and
adapted for providing sensing signals for the closed-loop
temperature control mechanism.
5. An ablation catheter as in claim 2, wherein the needles on the
at least one electrode is made of a material selected from the
group of platinum, iridium, gold, silver, stainless steel, and
Nitinol.
6. An ablation catheter as in claim 2 further comprising a coating
of heparin on an exterior surface of the inner catheter to enhance
biocompatibility.
7. An ablation catheter as in claim 2 further comprising a
treatment on an exterior surface of the inner catheter with low
surface energy substrates of fluorinated polymers to mitigate blood
coagulation.
8. An ablation catheter as in claim 2 further comprising ultrasonic
probes on a same side of the needles on the at least one electrode
adapted for ultrasonic signals being directed outwardly and
received inwardly relative to the at least one electrode to permit
rapid and substantially continuous viewing of a target tissue.
9. An ablation catheter as in claim 2 further comprising a
plurality of ultrasonic visible markers being disposed in close
proximity to the plurality of needles on the at least one
electrode.
10. A tissue ablation system using an ablation catheter
comprising:
a delivery catheter having a distal end, a proximal end, and at
least one lumen extending between the distal end and the proximal
end;
a handle attached to the proximal end of the delivery catheter;
an inner catheter located within the at least one lumen of the
delivery catheter, the inner catheter having a distal tip section,
a distal end, a proximal end, and a central lumen extending between
the distal end and the proximal end of the inner catheter, wherein
the distal tip section having at least one electrode;
a plurality of needles on the at least one electrode, each having a
tip, wherein a longitudinal length of said at least one electrode
is 4 mm or longer, a distance between the tips of the needles is 2
mm or less, a height of each needle is 1 mm or less, and wherein
the plurality of needles on the at least one electrode face a
target tissue side; and
a RF current generator, wherein a RF current is delivered from the
RF current generator to the plurality of needles on the at least
one electrode.
Description
FIELD OF THE INVENTION
The present invention generally relates to improved constructions
for a cardiovascular catheter. More particularly, this invention
relates to apparatus and methods for ablating cardiac arrhythmias
via a steerable ablation catheter having a plurality of needles on
at least one electrode for ablating intracardiac tissues resulting
in a plurality of deeper and larger lesions in the myocardium or
epicardium of the heart.
BACKGROUND OF THE INVENTION
Symptoms of abnormal heart rhythms are generally referred to as
cardiac arrhythmias, with an abnormally rapid rhythm being referred
to as a tachycardia. The present invention is concerned with the
treatment of tachycardias which are frequently caused by the
presence of an "arrhythmogenic site" or "accessory atrioventricular
pathway" close to the inner surface of the chambers of a heart. The
heart includes a number of normal pathways which are responsible
for the propagation of electrical signals from upper to lower
chamber necessary for performing normal systole and diastole
function. The presence of arrhythmogenic site or accessory pathway
can bypass or short circuit the normal pathway, potentially
resulting in very rapid heart contractions, referred to here as
tachycardias.
Treatment of tachycardias may be accomplished by a variety of
approaches, including drugs, surgery, implantable
pacemakers/defibrillators, and catheter ablation. While drugs may
be the treatment of choice for many patients, they only mask the
symptoms and do not cure the underlying causes. Implantable devices
only correct the arrhythmia after it occurs. Surgical and
catheter-based treatments, in contrast, will actually cure the
problem, usually by ablating the abnormal arrhythmogenic tissue or
accessory pathway responsible for the tachycardia. It is important
for a physician to accurately steer the catheter to the exact site
for ablation. Once at the site, it is important for a physician to
control the emission of energy to ablate the tissue within the
heart.
Of particular interest to the present invention are radiofrequency
(RF) ablation protocols which have proven to be highly effective in
tachycardia treatment while exposing a patient to minimal side
effects and risks. Radiofrequency catheter ablation is generally
performed after conducting an initial mapping study where the
locations of the arrhythmogenic site and/or accessory pathway are
determined. After a mapping study, an ablation catheter is usually
introduced to the target heart chamber and is manipulated so that
the ablation tip electrode lies exactly at the target tissue site.
Radiofrequency energy or other suitable energy is then applied
through the tip electrode to the cardiac tissue in order to ablate
the tissue of arrhythmogenic site or the accessory pathway. By
successfully destroying that tissue, the abnormal signal patterns
responsible for the tachycardia may be eliminated. However, in the
case of atrial fibrillation (AFib), multiple arrhythmogenic sites
and/or multiple accessory pathways exist. The conventional catheter
with a single ablation tip electrode can not effectively cure the
symptoms.
Atrial fibrillation is believed to be the result of the
simultaneous occurrence of multiple wavelets of functional re-entry
of electrical impulses within the atria, resulting in a condition
in which the transmission of electrical activity becomes so
disorganized that the atria contracts irregularly. Once considered
a benign disorder, AFib now is widely recognized as the cause of
significant morbidity and mortality. The most dangerous outcome
from AFib is thromboembolism and stroke risk, the latter due to the
chaotic contractions of the atria causing blood to pool. This in
turn can lead to clot formation and the potential for an embolic
stroke. According to data from the American Heart Association,
about 75,000 strokes per year is AFib-related.
A catheter utilized in the radiofrequency ablation is inserted into
a major vein or artery, usually in the neck or groin area. The tip
section of a catheter is referred to here as the portion of that
catheter shaft containing the electrode or electrodes which may be
deflectable. The catheter is then guided into the appropriate
chamber of the heart by appropriate manipulation through the vein
or artery. The tip of a catheter must be manipulatable by a
physician from the proximal end of the catheter, so that the
electrode at the tip section can be positioned against the tissue
site to be ablated. The catheter must have a great deal of
flexibility in order to follow the pathway of major blood vessels
into the heart. It must permit user manipulation of the tip even
when the catheter body is in a curved and twisted configuration.
The tip section of a conventional electrophysiology catheter that
is deflectable usually contains one large electrode about 4 mm in
length for ablation purpose. The lesion is generally not deep
because of a flat contact surface.
After the exact location of a target tissue is identified, the
ablation apparatus may still not easily approach the target site
even with assistance of an internal viewing means, such as an
endoscope. This viewing situation may turn into a nightmare when an
endoscope approach becomes prohibitive or unavailable during
procedures. An external ultrasonic imaging capability therefore
becomes in need so that ablation is not taking place in an
inappropriate location. In the U.S. Pat. No. 4,794,931, there has
been disclosed a catheter apparatus and system which can be
utilized for ultrasonic imaging. However, there is no disclosure to
how such an apparatus and system can be utilized in conjunction
with an endocardial ablation apparatus having electrodes comprising
a plurality of needles on at least one electrode to achieve the
desired ultrasonic imaging and ultimately the desired ablation.
Imran in U.S. Pat. No. 5,281,218 teaches a needle electrode
attached on a catheter for radiofrequency ablation. Though a needle
like electrode is beneficial to ablate a tissue point for deep
lesion, it is not possible to make a plurality of deeper and larger
lesions in a region such as in the case of atrial fibrillation or
in the case of epicardial side of the myocardium. For atrial
fibrillation treatment, the limitation of said technique is obvious
because of its single ablation point.
While a radiofrequency electrophysiology ablation procedure using
an existing catheter has had promising results, the tip section of
a known catheter usually have only one large electrode or one
needle electrode for ablation purpose. Therefore there is a need
for a new and improved catheter for making a plurality of deeper
and larger lesions in the myocardium or epicardium of the
heart.
SUMMARY OF THE INVENTION
In general, it is an object of the present invention to provide an
improved ablation catheter with a plurality of needles on at least
one electrode which can be used in ablating the arrhythmogenic
region instead of an arrhythmogenic point of a patient. This
catheter is particularly useful for treating the patient with
atrial fibrillation (AFib) indications. In one embodiment, an
ablation catheter comprises a delivery catheter having a distal
end, a proximal end and at least one lumen extending therebetween.
A handle is attached to the proximal end of said delivery
catheter.
The delivery catheter has an electrode deployment means. The
electrode deployment means includes a retractable inner catheter
having a tip section, comprising a plurality of needles on at least
one electrode. The inner catheter comprises a distal end, a
proximal end, and a central lumen extending therebetween. The
proximal end is attached to the electrode deployment means which
has a push-pull type mechanism on the handle. In one embodiment,
the at least one electrode becomes the tip electrode while a
plurality of band electrodes spaced at a pre-determined distance
from the preceding electrode. In an alternate embodiment, the at
least one electrode contains a plurality of needles on said
electrode. In a further embodiment, the plurality of needles on at
least one electrode faces outward toward the tissue surface to be
ablated. Therefore, at ablation time, the needles are positioned
essentially perpendicular to the tissues to be ablated. In still
another embodiment, the needles face at different directions so as
to contact the endocardial tissue when a bi-directional deflectable
catheter is used in the ablation procedure. The inner catheter has
a non-deployed state when it is positioned in the delivery
catheter. This non-deployed state is maintained during the ablation
catheter insertion operation into a patient and during withdrawal
of the catheter from a patient.
The ablation catheter further comprises a steering mechanism at the
handle for controlling the deflection of said at least one
electrode. Usually a rotating ring or a push-pull plunger is
employed in the steering mechanism. In another embodiment, the
steerable ablation catheter comprises a bidirectional deflection of
the tip section having a plurality of needles on the at least one
electrode. One end of the steering wire is attached at certain
point of the tip section of said inner catheter. The other end is
attached to the steering mechanism at the handle. The steering
mechanism on a steerable catheter or device is well known to those
who are skilled in the art.
The inner catheter has a deployed state when it is advanced out of
the distal end of said delivery catheter. Deployment of the inner
catheter is accomplished by a pushing action on the push-pull
deployment mechanism at the handle. In one embodiment, the tip
section of the deployed inner catheter has a preformed shape so
that the at least one electrode would extend outwardly of the
delivery catheter when deployed. The degree of deployment is
controlled by the pushing action at said push-pull mechanism on the
handle and is proportional to the push distance on the push-pull
plunger of the push-pull mechanism which is quantifiable.
The deployed inner catheter having the at least one electrode,
defines an ablation target. The sharp point of the needles of each
electrode is positioned at the forward side facing the target
tissue. After finishing the ablation operation, the retraction of
the inner catheter is accomplished by pulling back the inner
catheter relative to the delivery catheter. The degree of
retraction is mainly controlled by the pulling action at the
push-pull mechanism on the handle.
At least one conducting wire which is soldered to the electrode
passes through the lumen of the inner catheter and the interior
void of the handle and is thereafter soldered to a contact pin of
the connector secured at the proximal end of the handle. Therefrom,
the conducting wire is connected to an external RF generator for
ablation operations and/or to an EKG monitor for recording and
display of the endocardial electrical signal.
In an additional embodiment, the ablation system further comprises
a temperature sensing and closed-loop temperature control mechanism
for the electrode having at least one temperature sensor at the
tissue contact site of the electrodes. The location of the
temperature sensor is preferably in the proximity of one of the
needles of the electrodes.
In a particular embodiment, the length of the at least one
electrode is 4 mm or longer. In an alternate embodiment, the
needles on an electrode are equally spaced and the distance between
the needle tip of the at least one electrode is 2 mm or less. The
height of the needle is usually 1 mm or less. The material for the
at least one electrode may consist of conductive metals such as
platinum, iridium, gold, silver, stainless steel, Nitinol, or an
alloy of their mixture.
In a still further embodiment, the tip section of the inner
catheter comprising the electrodes is formed of a conducting
material without catheter shaft. The at least one electrode in this
embodiment is formed of a flexible metal mesh that can be retracted
into the delivery catheter during inserting and withdrawal of said
inner catheter system.
In order to provide increased torsional rigidity to the catheter
shaft, the shaft material preferably comprises a polymeric tube
having a Durometer in the range from 30D to 90D, usually from 40D
to 65D. Preferably, the shaft has a composite structure including a
base layer of a relatively low Durometer material, a stiffening
layer, for example, metal braid or coil, and an outer layer
comprising the biocompatible polymeric material or the material
that may render itself biocompatible by surface treatment. To
enhance biocompatibility, the catheter shaft further comprises
surface coating of heparin on the surface of the catheter shaft. It
is hypothesized that the coated heparin forms a barrier, while not
releasing heparin from said surface, between the blood and the
catheter surface to enhance biocompatibility during
electrophysiology procedures. In a further embodiment, an ablation
catheter further comprises surface treatment of low surface energy
substrates, such as Teflon.RTM. type fluorinated polymers, to
mitigate blood coagulation during high-energy ablation. Fluorinated
polymer can be deposited on the shaft surface via plasma coating
technology or the like.
A method for operating a steerable ablation catheter system having
a plurality of needles on at least one electrode at the tip section
of an deployable inner catheter within a heart chamber comprises
percutaneously introducing the delivery catheter through a blood
vessel to the heart chamber, wherein the at least one electrode is
deployed by pushing the inner catheter forward and forming the
desired electrode pre-shape; deflecting the distal section of the
inner catheter about a transverse axis to position the at least one
electrode near a target region on an interior wall of the heart
chamber; intimately contacting the electrode, including the
needles, with the intracardiac tissue; and applying radiofrequency
energy to the target location through the needles of this
invention.
Another object of the invention is to provide a catheter and
methods in which it is possible to view the area to be ablated
prior to ablation to ensure that ablation is being carried out in
an appropriate location. The electrode having a plurality of
needles is encoded with plurality of markers which are visible to
ultrasonic energy. The markers have been provided in the form of
encapsulated air bubbles. In another embodiment, probes with
ultrasonic signal capability are located adjacent to the needle of
said electrode. The ultrasonic signals are directed outwardly and
received inwardly relative to the front side of the electrode to
permit rapid and substantially continuous viewing of the target
tissue.
The method and apparatus of the present invention have several
significant advantages over known catheter or ablation techniques.
In particular, the at least one electrode having a plurality of
needles of a steerable ablation catheter of this invention may
result in a plurality of deeper, larger and contiguous lesions
which is highly desirable in the AFib treatment.
BRIEF DESCRIPTION OF THE DRAWINGS
Additional objects and features of the present invention will
become more apparent and the invention itself will be best
understood from the following Detailed Description of the Exemplary
Embodiments, when read with reference to the accompanying
drawings.
FIG. 1 is an overall view of a catheter having at least one
electrode comprising a plurality of needles constructed in
accordance with the principles of the present invention.
FIG. 2 is a close-up view of the distal section of the catheter at
non-deployed state.
FIG. 3 is a cross-sectional view of the tip section of the inner
catheter having at least one electrode comprising a plurality of
needles.
FIG. 4 is a perspective view of the tip section of the inner
catheter of FIG. 1.
FIG. 5 shows the contact of the at least one electrode of the
catheter of this invention with the tissue.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
FIG. 1 shows a perspective view of the catheter having a delivery
catheter. An ablation catheter constructed in accordance with the
principles of the present invention comprises a delivery catheter 1
having a distal end 7, a proximal end 10, and at least one lumen
therebetween. The delivery catheter comprises an electrode
deployment means, wherein the deployment means comprises a
retractable inner catheter 2 having a tip section, comprising a
plurality of needles on at least one electrode. A handle 4 is
attached to the proximal end 10 of said delivery catheter 1.
The connector 3 secured at the proximal end of the catheter is part
of the handle section 4. The handle has one steering mechanism 5
and one inner catheter deployment mechanism 6. The steering
mechanism 5 is to deflect the tip section of the inner catheter 2
when the tip section is deployed outside of the distal end 7 of
said delivery catheter 1. By pushing the front plunger 8 of the
handle 4, the tip section of the inner catheter deflects to one
direction. By pulling the front plunger 8, the tip section returns
to its neutral position.
The deployment mechanism 6 constitutes a catheter shaft for the
inner catheter, wherein the catheter shaft resists buckling inside
the delivery catheter 1 and inside the cavity of the handle 4. The
rear plunger 9 is used to push the tip section of the inner
catheter 2 outwards of the delivery catheter 1 for ablation
purpose. While the catheter is introduced into the body or removed
from the body, the tip section of the inner catheter 2 is retracted
into the delivery catheter 1 by pulling back the rear plunger
9.
FIG. 2 shows a close-up view of the distal section of the catheter
at non-deployed state of FIG. 1. The tip section of the delivery
catheter comprises a distal end 7 and a sealable opening 11. The
tip section of the inner catheter 2 comprises a tip electrode 12
which has a plurality of needles 13, and at least one band
electrode 14 which has a plurality of needles 15. The electrodes
are formed of a conducting material. In one embodiment, at least
one electrode is a metal mesh securely wrapped outside of the
catheter shaft of the inner catheter 2, wherein the electrode has a
plurality of needles 14 or 15.
FIG. 3 shows a cross-sectional view of the tip section with at
least one temperature sensor 17 and ultrasonic imaging
capabilities. In order to enhance the ablation positioning of said
ablation catheter; the electrode is encoded with markers 19 which
are visible to ultrasonic energy. Such markers 19 are provided in
the form of encapsulated air bubbles. Several markers 19 are placed
on the same side of the needles and in the proximity of the needles
15 of the at least one electrode 14 in a way so that the exact
location of the needles 15 is visible to an external ultrasonic
energy. By way of example, the bubble in a marker can be formed by
introducing air by a syringe (not shown) penetrating the wall of
the plastic front body of said electrode and thereafter is sealed
by epoxy.
The at least one electrode comprising a plurality of needles has an
insulated conducting wire 16 which passes through the lumen of the
inner catheter 2 and is soldered to a contact pin of the connector
3 at the proximal end of the handle 4. The conducting wire from the
connector end is externally connected to an EKG for diagnosis or to
a RF current generator during an electrophysiology ablation
procedure. Therefrom, the RF energy is transmitted through the
conducting wire to the at least one electrode and delivered the
energy to the target tissue.
A temperature sensor 17, either a thermocouple or a thermister, is
constructed at the proximity of one needle 13 or 15 of the
electrodes 12 or 14 to measure the tissue contact temperature when
RF energy is delivered. The temperature sensing wire 18 from the
thermocouple or thermister is connected to one of the contact pins
(not shown) of the connector 3 and externally connected to a
transducer and to a temperature controller. The temperature reading
is thereafter relayed to a close-loop control mechanism to adjust
the RF energy output. The RF energy delivered is thus controlled by
the temperature sensor reading or by the pre-programmed control
mechanism.
The tip section having a plurality of needles on the at least one
electrode formed of conducting material can be extended out of the
delivery catheter 1 and retracted into said delivery catheter by a
deployment mechanism 6 at the handle 4. To prevent blood from
backflow into the delivery catheter 1, a silicone type sealer 11 is
installed at certain opening of the delivery catheter between the
delivery catheter 1 and the inner catheter 2.
FIG. 4 shows a perspective view of the tip section of the inner
catheter, wherein the tip section comprises a plurality of
electrodes having a plurality of needles secured onto the
electrode. For the steering mechanism 5, a steering wire is firmly
attached onto a flat wire or coil spring (not shown) at the distal
contact point of said flat wire. The proximal end of the steering
wire is secured to the push-pull plunger 8 of the steering
mechanism. By pushing or pulling the steering wire from the handle,
the distal portion of the inner catheter 2 deflects to one
direction.
FIG. 5 shows the contact of the needles 13 and 15 of the at least
one electrodes 12 and 14 with the target tissue 20. The needle may
contact the tissue at an angle essentially perpendicular to the
target tissue. RF energy is applied thereafter and a plurality of
deep and large lesions are created which are contiguous for the
treatment of a tachycardia.
From the foregoing, it should now be appreciated that an improved
ablation catheter having a plurality of needles on the at least one
electrode and a steerable mechanism has been disclosed for ablation
procedures, including endocardial and body tissue ablations. While
the invention has been described with reference to a specific
embodiment, the description is illustrative of the invention and is
not to be construed as limiting the invention. Various
modifications and applications may occur to those skilled in the
art without departing from the true spirit and scope of the
invention as described by the appended claims.
* * * * *